So I've been taking ballroom dancing lessons with my boyfriend and we were trying to do an overhead lift (similar to Dirty Dancing). He can get me up without a problem and we can hold it with no hands on his shoulders for a very brief period but then I start falling forward and he has to lower me down.

Does anyone have any idea why this might be happening? I'm assuming it's a form/technique issue since he's strong enough to easily hold me up much longer.